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                <ol class="chapter"><li class="chapter-item expanded affix "><a href="../../PREFACE.html">前言</a></li><li class="chapter-item expanded affix "><li class="part-title">快速上手</li><li class="chapter-item expanded "><a href="../../zh/tutorials/index.html"><strong aria-hidden="true">1.</strong> 快速上手</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/tutorials/typescript-in-5-minutes.html"><strong aria-hidden="true">1.1.</strong> 5 分钟了解 TypeScript</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/asp.net-core.html"><strong aria-hidden="true">1.2.</strong> ASP.NET Core</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/asp.net-4.html"><strong aria-hidden="true">1.3.</strong> ASP.NET 4</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/gulp.html"><strong aria-hidden="true">1.4.</strong> Gulp</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/knockout.html"><strong aria-hidden="true">1.5.</strong> Knockout.js</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/react-and-webpack.html"><strong aria-hidden="true">1.6.</strong> React 与 webpack</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/react.html"><strong aria-hidden="true">1.7.</strong> React</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/angular-2.html"><strong aria-hidden="true">1.8.</strong> Angular 2</a></li><li class="chapter-item expanded "><a href="../../zh/tutorials/migrating-from-javascript.html"><strong aria-hidden="true">1.9.</strong> 从 JavaScript 迁移到 TypeScript</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">手册</li><li class="chapter-item expanded "><a href="../../zh/handbook/index.html"><strong aria-hidden="true">2.</strong> 手册</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/handbook/basic-types.html"><strong aria-hidden="true">2.1.</strong> 基础类型</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/interfaces.html"><strong aria-hidden="true">2.2.</strong> 接口</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/functions.html"><strong aria-hidden="true">2.3.</strong> 函数</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/literal-types.html"><strong aria-hidden="true">2.4.</strong> 字面量类型</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/unions-and-intersections.html"><strong aria-hidden="true">2.5.</strong> 联合类型和交叉类型</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/classes.html"><strong aria-hidden="true">2.6.</strong> 类</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/enums.html"><strong aria-hidden="true">2.7.</strong> 枚举</a></li><li class="chapter-item expanded "><a href="../../zh/handbook/generics.html"><strong aria-hidden="true">2.8.</strong> 泛型</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">手册（进阶）</li><li class="chapter-item expanded "><a href="../../zh/reference/index.html"><strong aria-hidden="true">3.</strong> 手册（进阶）</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/reference/advanced-types.html"><strong aria-hidden="true">3.1.</strong> 高级类型</a></li><li class="chapter-item expanded "><a href="../../zh/reference/utility-types.html" class="active"><strong aria-hidden="true">3.2.</strong> 实用工具类型</a></li><li class="chapter-item expanded "><a href="../../zh/reference/decorators.html"><strong aria-hidden="true">3.3.</strong> Decorators</a></li><li class="chapter-item expanded "><a href="../../zh/reference/declaration-merging.html"><strong aria-hidden="true">3.4.</strong> 声明合并</a></li><li class="chapter-item expanded "><a href="../../zh/reference/iterators-and-generators.html"><strong aria-hidden="true">3.5.</strong> Iterators 和 Generators</a></li><li class="chapter-item expanded "><a href="../../zh/reference/jsx.html"><strong aria-hidden="true">3.6.</strong> JSX</a></li><li class="chapter-item expanded "><a href="../../zh/reference/mixins.html"><strong aria-hidden="true">3.7.</strong> 混入</a></li><li class="chapter-item expanded "><a href="../../zh/reference/modules.html"><strong aria-hidden="true">3.8.</strong> 模块</a></li><li class="chapter-item expanded "><a href="../../zh/reference/module-resolution.html"><strong aria-hidden="true">3.9.</strong> 模块解析</a></li><li class="chapter-item expanded "><a href="../../zh/reference/namespaces.html"><strong aria-hidden="true">3.10.</strong> 命名空间</a></li><li class="chapter-item expanded "><a href="../../zh/reference/namespaces-and-modules.html"><strong aria-hidden="true">3.11.</strong> 命名空间和模块</a></li><li class="chapter-item expanded "><a href="../../zh/reference/symbols.html"><strong aria-hidden="true">3.12.</strong> Symbols</a></li><li class="chapter-item expanded "><a href="../../zh/reference/triple-slash-directives.html"><strong aria-hidden="true">3.13.</strong> 三斜线指令</a></li><li class="chapter-item expanded "><a href="../../zh/reference/type-compatibility.html"><strong aria-hidden="true">3.14.</strong> 类型兼容性</a></li><li class="chapter-item expanded "><a href="../../zh/reference/type-inference.html"><strong aria-hidden="true">3.15.</strong> 类型推论</a></li><li class="chapter-item expanded "><a href="../../zh/reference/variable-declarations.html"><strong aria-hidden="true">3.16.</strong> 变量声明</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">手册（v2）</li><li class="chapter-item expanded "><a href="../../zh/handbook-v2/index.html"><strong aria-hidden="true">4.</strong> 手册（v2）</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/handbook-v2/type-manipulation/template-literal-types.html"><strong aria-hidden="true">4.1.</strong> 模版字面量类型</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">TypeScript 声明文件（.d.ts）</li><li class="chapter-item expanded "><a href="../../zh/declaration-files/index.html"><strong aria-hidden="true">5.</strong> 如何书写声明文件</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/declaration-files/introduction.html"><strong aria-hidden="true">5.1.</strong> 介绍</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/by-example.html"><strong aria-hidden="true">5.2.</strong> 举例</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/library-structures.html"><strong aria-hidden="true">5.3.</strong> 库结构</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/templates.html"><strong aria-hidden="true">5.4.</strong> 模板</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/do-s-and-don-ts.html"><strong aria-hidden="true">5.5.</strong> 最佳实践</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/deep-dive.html"><strong aria-hidden="true">5.6.</strong> 深入</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/publishing.html"><strong aria-hidden="true">5.7.</strong> 发布</a></li><li class="chapter-item expanded "><a href="../../zh/declaration-files/consumption.html"><strong aria-hidden="true">5.8.</strong> 使用</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">TypeScript for JavaScript</li><li class="chapter-item expanded "><a href="../../zh/javascript/type-checking-javascript-files.html"><strong aria-hidden="true">6.</strong> JavaScript 文件里的类型检查</a></li><li class="chapter-item expanded affix "><li class="part-title">工程配置</li><li class="chapter-item expanded "><a href="../../zh/project-config/index.html"><strong aria-hidden="true">7.</strong> 工程配置</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/project-config/tsconfig.json.html"><strong aria-hidden="true">7.1.</strong> tsconfig.json</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/project-references.html"><strong aria-hidden="true">7.2.</strong> 工程引用</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/typings-for-npm-packages.html"><strong aria-hidden="true">7.3.</strong> NPM 包的类型</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/compiler-options.html"><strong aria-hidden="true">7.4.</strong> 编译选项</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/configuring-watch.html"><strong aria-hidden="true">7.5.</strong> 配置 Watch</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/compiler-options-in-msbuild.html"><strong aria-hidden="true">7.6.</strong> 在 MSBuild 里使用编译选项</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/integrating-with-build-tools.html"><strong aria-hidden="true">7.7.</strong> 与其它构建工具整合</a></li><li class="chapter-item expanded "><a href="../../zh/project-config/nightly-builds.html"><strong aria-hidden="true">7.8.</strong> 使用 TypeScript 的每日构建版本</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">版本发布说明（Release Notes）</li><li class="chapter-item expanded "><a href="../../zh/release-notes/index.html"><strong aria-hidden="true">8.</strong> 新增功能</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-5.4.html"><strong aria-hidden="true">8.1.</strong> TypeScript 5.4</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-5.3.html"><strong aria-hidden="true">8.2.</strong> TypeScript 5.3</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-5.2.html"><strong aria-hidden="true">8.3.</strong> TypeScript 5.2</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-5.1.html"><strong aria-hidden="true">8.4.</strong> TypeScript 5.1</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-5.0.html"><strong aria-hidden="true">8.5.</strong> TypeScript 5.0</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.9.html"><strong aria-hidden="true">8.6.</strong> TypeScript 4.9</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.8.html"><strong aria-hidden="true">8.7.</strong> TypeScript 4.8</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.7.html"><strong aria-hidden="true">8.8.</strong> TypeScript 4.7</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.6.html"><strong aria-hidden="true">8.9.</strong> TypeScript 4.6</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.5.html"><strong aria-hidden="true">8.10.</strong> TypeScript 4.5</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.4.html"><strong aria-hidden="true">8.11.</strong> TypeScript 4.4</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.3.html"><strong aria-hidden="true">8.12.</strong> TypeScript 4.3</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.2.html"><strong aria-hidden="true">8.13.</strong> TypeScript 4.2</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.1.html"><strong aria-hidden="true">8.14.</strong> TypeScript 4.1</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-4.0.html"><strong aria-hidden="true">8.15.</strong> TypeScript 4.0</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.9.html"><strong aria-hidden="true">8.16.</strong> TypeScript 3.9</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.8.html"><strong aria-hidden="true">8.17.</strong> TypeScript 3.8</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.7.html"><strong aria-hidden="true">8.18.</strong> TypeScript 3.7</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.6.html"><strong aria-hidden="true">8.19.</strong> TypeScript 3.6</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.5.html"><strong aria-hidden="true">8.20.</strong> TypeScript 3.5</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.4.html"><strong aria-hidden="true">8.21.</strong> TypeScript 3.4</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.3.html"><strong aria-hidden="true">8.22.</strong> TypeScript 3.3</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.2.html"><strong aria-hidden="true">8.23.</strong> TypeScript 3.2</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.1.html"><strong aria-hidden="true">8.24.</strong> TypeScript 3.1</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-3.0.html"><strong aria-hidden="true">8.25.</strong> TypeScript 3.0</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.9.html"><strong aria-hidden="true">8.26.</strong> TypeScript 2.9</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.8.html"><strong aria-hidden="true">8.27.</strong> TypeScript 2.8</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.7.html"><strong aria-hidden="true">8.28.</strong> TypeScript 2.7</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.6.html"><strong aria-hidden="true">8.29.</strong> TypeScript 2.6</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.5.html"><strong aria-hidden="true">8.30.</strong> TypeScript 2.5</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.4.html"><strong aria-hidden="true">8.31.</strong> TypeScript 2.4</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.3.html"><strong aria-hidden="true">8.32.</strong> TypeScript 2.3</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.2.html"><strong aria-hidden="true">8.33.</strong> TypeScript 2.2</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.1.html"><strong aria-hidden="true">8.34.</strong> TypeScript 2.1</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-2.0.html"><strong aria-hidden="true">8.35.</strong> TypeScript 2.0</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.8.html"><strong aria-hidden="true">8.36.</strong> TypeScript 1.8</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.7.html"><strong aria-hidden="true">8.37.</strong> TypeScript 1.7</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.6.html"><strong aria-hidden="true">8.38.</strong> TypeScript 1.6</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.5.html"><strong aria-hidden="true">8.39.</strong> TypeScript 1.5</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.4.html"><strong aria-hidden="true">8.40.</strong> TypeScript 1.4</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.3.html"><strong aria-hidden="true">8.41.</strong> TypeScript 1.3</a></li><li class="chapter-item expanded "><a href="../../zh/release-notes/typescript-1.1.html"><strong aria-hidden="true">8.42.</strong> TypeScript 1.1</a></li></ol></li><li class="chapter-item expanded "><li class="part-title">破坏性改动（Breaking Changes）</li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/index.html"><strong aria-hidden="true">9.</strong> Breaking Changes</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.6.html"><strong aria-hidden="true">9.1.</strong> TypeScript 3.6</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.5.html"><strong aria-hidden="true">9.2.</strong> TypeScript 3.5</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.4.html"><strong aria-hidden="true">9.3.</strong> TypeScript 3.4</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.2.html"><strong aria-hidden="true">9.4.</strong> TypeScript 3.2</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.1.html"><strong aria-hidden="true">9.5.</strong> TypeScript 3.1</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-3.0.html"><strong aria-hidden="true">9.6.</strong> TypeScript 3.0</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.9.html"><strong aria-hidden="true">9.7.</strong> TypeScript 2.9</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.8.html"><strong aria-hidden="true">9.8.</strong> TypeScript 2.8</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.7.html"><strong aria-hidden="true">9.9.</strong> TypeScript 2.7</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.6.html"><strong aria-hidden="true">9.10.</strong> TypeScript 2.6</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.4.html"><strong aria-hidden="true">9.11.</strong> TypeScript 2.4</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.3.html"><strong aria-hidden="true">9.12.</strong> TypeScript 2.3</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.2.html"><strong aria-hidden="true">9.13.</strong> TypeScript 2.2</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.1.html"><strong aria-hidden="true">9.14.</strong> TypeScript 2.1</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-2.0.html"><strong aria-hidden="true">9.15.</strong> TypeScript 2.0</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-1.8.html"><strong aria-hidden="true">9.16.</strong> TypeScript 1.8</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-1.7.html"><strong aria-hidden="true">9.17.</strong> TypeScript 1.7</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-1.6.html"><strong aria-hidden="true">9.18.</strong> TypeScript 1.6</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-1.5.html"><strong aria-hidden="true">9.19.</strong> TypeScript 1.5</a></li><li class="chapter-item expanded "><a href="../../zh/breaking-changes/typescript-1.4.html"><strong aria-hidden="true">9.20.</strong> TypeScript 1.4</a></li></ol></li></ol>
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                        <h1 id="实用工具类型"><a class="header" href="#实用工具类型">实用工具类型</a></h1>
<p>TypeScript 提供一些工具类型来帮助常见的类型转换。这些类型是全局可见的。</p>
<h2 id="目录"><a class="header" href="#目录">目录</a></h2>
<ul>
<li><a href="#partialtype"><code>Partial&lt;T&gt;</code>，TypeScript 2.1</a></li>
<li><a href="#readonlytype"><code>Readonly&lt;Type&gt;</code>，TypeScript 2.1</a></li>
<li><a href="#recordkeys-type"><code>Record&lt;Keys, Type&gt;</code>，TypeScript 2.1</a></li>
<li><a href="#picktype-keys"><code>Pick&lt;Type, Keys&gt;</code>，TypeScript 2.1</a></li>
<li><a href="#omittype-keys"><code>Omit&lt;Type, Keys&gt;</code>，TypeScript 3.5</a></li>
<li><a href="#excludetype-excludedunion"><code>Exclude&lt;Type, ExcludedUnion&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#extracttype-union"><code>Extract&lt;Type, Union&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#nonnullabletype"><code>NonNullable&lt;Type&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#parameterstype"><code>Parameters&lt;Type&gt;</code></a></li>
<li><a href="#constructorparameterstype"><code>ConstructorParameters&lt;Type&gt;</code></a></li>
<li><a href="#returntypetype"><code>ReturnType&lt;Type&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#instancetypetype"><code>InstanceType&lt;Type&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#requiredtype"><code>Required&lt;Type&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#thisparametertypetype"><code>ThisParameterType&lt;Type&gt;</code></a></li>
<li><a href="#omitthisparametertype"><code>OmitThisParameter&lt;Type&gt;</code></a></li>
<li><a href="#thistypetype"><code>ThisType&lt;Type&gt;</code>，TypeScript 2.8</a></li>
<li><a href="#%E6%93%8D%E4%BD%9C%E5%AD%97%E7%AC%A6%E4%B8%B2%E7%9A%84%E7%B1%BB%E5%9E%8B">操作字符串的类型</a></li>
</ul>
<h2 id="partialtype"><a class="header" href="#partialtype"><code>Partial&lt;Type&gt;</code></a></h2>
<p>构造类型<code>Type</code>，并将它所有的属性设置为可选的。它的返回类型表示输入类型的所有子类型。</p>
<h3 id="例子"><a class="header" href="#例子">例子</a></h3>
<pre><code class="language-typescript">interface Todo {
    title: string;
    description: string;
}

function updateTodo(todo: Todo, fieldsToUpdate: Partial&lt;Todo&gt;) {
    return { ...todo, ...fieldsToUpdate };
}

const todo1 = {
    title: 'organize desk',
    description: 'clear clutter',
};

const todo2 = updateTodo(todo1, {
    description: 'throw out trash',
});
</code></pre>
<h2 id="readonlytype"><a class="header" href="#readonlytype"><code>Readonly&lt;Type&gt;</code></a></h2>
<p>构造类型<code>Type</code>，并将它所有的属性设置为<code>readonly</code>，也就是说构造出的类型的属性不能被再次赋值。</p>
<h3 id="例子-1"><a class="header" href="#例子-1">例子</a></h3>
<pre><code class="language-typescript">interface Todo {
    title: string;
}

const todo: Readonly&lt;Todo&gt; = {
    title: 'Delete inactive users',
};

todo.title = 'Hello'; // Error: cannot reassign a readonly property
</code></pre>
<p>这个工具可用来表示在运行时会失败的赋值表达式（比如，当尝试给<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze">冻结对象</a>的属性再次赋值时）。</p>
<h3 id="objectfreeze"><a class="header" href="#objectfreeze"><code>Object.freeze</code></a></h3>
<pre><code class="language-typescript">function freeze&lt;T&gt;(obj: T): Readonly&lt;T&gt;;
</code></pre>
<h2 id="recordkeys-type"><a class="header" href="#recordkeys-type"><code>Record&lt;Keys, Type&gt;</code></a></h2>
<p>构造一个类型，其属性名的类型为<code>K</code>，属性值的类型为<code>T</code>。这个工具可用来将某个类型的属性映射到另一个类型上。</p>
<h3 id="例子-2"><a class="header" href="#例子-2">例子</a></h3>
<pre><code class="language-typescript">interface PageInfo {
    title: string;
}

type Page = 'home' | 'about' | 'contact';

const x: Record&lt;Page, PageInfo&gt; = {
    about: { title: 'about' },
    contact: { title: 'contact' },
    home: { title: 'home' },
};
</code></pre>
<h2 id="picktype-keys"><a class="header" href="#picktype-keys"><code>Pick&lt;Type, Keys&gt;</code></a></h2>
<p>从类型<code>Type</code>中挑选部分属性<code>Keys</code>来构造类型。</p>
<h3 id="例子-3"><a class="header" href="#例子-3">例子</a></h3>
<pre><code class="language-typescript">interface Todo {
    title: string;
    description: string;
    completed: boolean;
}

type TodoPreview = Pick&lt;Todo, 'title' | 'completed'&gt;;

const todo: TodoPreview = {
    title: 'Clean room',
    completed: false,
};
</code></pre>
<h2 id="omittype-keys"><a class="header" href="#omittype-keys"><code>Omit&lt;Type, Keys&gt;</code></a></h2>
<p>从类型<code>Type</code>中获取所有属性，然后从中剔除<code>Keys</code>属性后构造一个类型。</p>
<h3 id="例子-4"><a class="header" href="#例子-4">例子</a></h3>
<pre><code class="language-typescript">interface Todo {
    title: string;
    description: string;
    completed: boolean;
}

type TodoPreview = Omit&lt;Todo, 'description'&gt;;

const todo: TodoPreview = {
    title: 'Clean room',
    completed: false,
};
</code></pre>
<h2 id="excludetype-excludedunion"><a class="header" href="#excludetype-excludedunion"><code>Exclude&lt;Type, ExcludedUnion&gt;</code></a></h2>
<p>从类型<code>Type</code>中剔除所有可以赋值给<code>ExcludedUnion</code>的属性，然后构造一个类型。</p>
<h3 id="例子-5"><a class="header" href="#例子-5">例子</a></h3>
<pre><code class="language-typescript">type T0 = Exclude&lt;'a' | 'b' | 'c', 'a'&gt;; // "b" | "c"
type T1 = Exclude&lt;'a' | 'b' | 'c', 'a' | 'b'&gt;; // "c"
type T2 = Exclude&lt;string | number | (() =&gt; void), Function&gt;; // string | number
</code></pre>
<h2 id="extracttype-union"><a class="header" href="#extracttype-union"><code>Extract&lt;Type, Union&gt;</code></a></h2>
<p>从类型<code>Type</code>中提取所有可以赋值给<code>Union</code>的类型，然后构造一个类型。</p>
<h3 id="例子-6"><a class="header" href="#例子-6">例子</a></h3>
<pre><code class="language-typescript">type T0 = Extract&lt;'a' | 'b' | 'c', 'a' | 'f'&gt;; // "a"
type T1 = Extract&lt;string | number | (() =&gt; void), Function&gt;; // () =&gt; void
</code></pre>
<h2 id="nonnullabletype"><a class="header" href="#nonnullabletype"><code>NonNullable&lt;Type&gt;</code></a></h2>
<p>从类型<code>Type</code>中剔除<code>null</code>和<code>undefined</code>，然后构造一个类型。</p>
<h3 id="例子-7"><a class="header" href="#例子-7">例子</a></h3>
<pre><code class="language-typescript">type T0 = NonNullable&lt;string | number | undefined&gt;; // string | number
type T1 = NonNullable&lt;string[] | null | undefined&gt;; // string[]
</code></pre>
<h2 id="parameterstype"><a class="header" href="#parameterstype"><code>Parameters&lt;Type&gt;</code></a></h2>
<p>由函数类型<code>Type</code>的参数类型来构建出一个元组类型。</p>
<h3 id="例子-8"><a class="header" href="#例子-8">例子</a></h3>
<pre><code class="language-ts">declare function f1(arg: { a: number; b: string }): void;

type T0 = Parameters&lt;() =&gt; string&gt;;
//    []
type T1 = Parameters&lt;(s: string) =&gt; void&gt;;
//    [s: string]
type T2 = Parameters&lt;&lt;T&gt;(arg: T) =&gt; T&gt;;
//    [arg: unknown]
type T3 = Parameters&lt;typeof f1&gt;;
//    [arg: { a: number; b: string; }]
type T4 = Parameters&lt;any&gt;;
//    unknown[]
type T5 = Parameters&lt;never&gt;;
//    never
type T6 = Parameters&lt;string&gt;;
//   never
//   Type 'string' does not satisfy the constraint '(...args: any) =&gt; any'.
type T7 = Parameters&lt;Function&gt;;
//   never
//   Type 'Function' does not satisfy the constraint '(...args: any) =&gt; any'.
</code></pre>
<h2 id="constructorparameterstype"><a class="header" href="#constructorparameterstype"><code>ConstructorParameters&lt;Type&gt;</code></a></h2>
<p>由构造函数类型来构建出一个元组类型或数组类型。
由构造函数类型<code>Type</code>的参数类型来构建出一个元组类型。（若<code>Type</code>不是构造函数类型，则返回<code>never</code>）。</p>
<h3 id="例子-9"><a class="header" href="#例子-9">例子</a></h3>
<pre><code class="language-ts">type T0 = ConstructorParameters&lt;ErrorConstructor&gt;;
//    [message?: string | undefined]
type T1 = ConstructorParameters&lt;FunctionConstructor&gt;;
//    string[]
type T2 = ConstructorParameters&lt;RegExpConstructor&gt;;
//    [pattern: string | RegExp, flags?: string | undefined]
type T3 = ConstructorParameters&lt;any&gt;;
//   unknown[]

type T4 = ConstructorParameters&lt;Function&gt;;
//    never
// Type 'Function' does not satisfy the constraint 'new (...args: any) =&gt; any'.
</code></pre>
<h2 id="returntypetype"><a class="header" href="#returntypetype"><code>ReturnType&lt;Type&gt;</code></a></h2>
<p>由函数类型<code>Type</code>的返回值类型构建一个新类型。</p>
<h3 id="例子-10"><a class="header" href="#例子-10">例子</a></h3>
<pre><code>type T0 = ReturnType&lt;() =&gt; string&gt;;  // string
type T1 = ReturnType&lt;(s: string) =&gt; void&gt;;  // void
type T2 = ReturnType&lt;(&lt;T&gt;() =&gt; T)&gt;;  // {}
type T3 = ReturnType&lt;(&lt;T extends U, U extends number[]&gt;() =&gt; T)&gt;;  // number[]
type T4 = ReturnType&lt;typeof f1&gt;;  // { a: number, b: string }
type T5 = ReturnType&lt;any&gt;;  // any
type T6 = ReturnType&lt;never&gt;;  // any
type T7 = ReturnType&lt;string&gt;;  // Error
type T8 = ReturnType&lt;Function&gt;;  // Error
</code></pre>
<h2 id="instancetypetype"><a class="header" href="#instancetypetype"><code>InstanceType&lt;Type&gt;</code></a></h2>
<p>由构造函数类型<code>Type</code>的实例类型来构建一个新类型。</p>
<h3 id="例子-11"><a class="header" href="#例子-11">例子</a></h3>
<pre><code class="language-typescript">class C {
    x = 0;
    y = 0;
}

type T0 = InstanceType&lt;typeof C&gt;; // C
type T1 = InstanceType&lt;any&gt;; // any
type T2 = InstanceType&lt;never&gt;; // any
type T3 = InstanceType&lt;string&gt;; // Error
type T4 = InstanceType&lt;Function&gt;; // Error
</code></pre>
<h2 id="requiredtype"><a class="header" href="#requiredtype"><code>Required&lt;Type&gt;</code></a></h2>
<p>构建一个类型，使类型<code>Type</code>的所有属性为<code>required</code>。
与此相反的是<a href="#partialtype"><code>Partial</code></a>。</p>
<h3 id="例子-12"><a class="header" href="#例子-12">例子</a></h3>
<pre><code class="language-typescript">interface Props {
    a?: number;
    b?: string;
}

const obj: Props = { a: 5 }; // OK

const obj2: Required&lt;Props&gt; = { a: 5 }; // Error: property 'b' missing
</code></pre>
<h2 id="thisparametertypetype"><a class="header" href="#thisparametertypetype"><code>ThisParameterType&lt;Type&gt;</code></a></h2>
<p>从函数类型中提取 <a href="../handbook/functions.html#this%E5%8F%82%E6%95%B0">this</a> 参数的类型。
若函数类型不包含 <code>this</code> 参数，则返回 <a href="../handbook/basic-types.html#unknown">unknown</a> 类型。</p>
<h3 id="例子-13"><a class="header" href="#例子-13">例子</a></h3>
<pre><code class="language-ts">function toHex(this: Number) {
    return this.toString(16);
}

function numberToString(n: ThisParameterType&lt;typeof toHex&gt;) {
    return toHex.apply(n);
}
</code></pre>
<h2 id="omitthisparametertype"><a class="header" href="#omitthisparametertype"><code>OmitThisParameter&lt;Type&gt;</code></a></h2>
<p>从<code>Type</code>类型中剔除 <a href="../handbook/functions.html#this%E5%8F%82%E6%95%B0"><code>this</code></a> 参数。
若未声明 <code>this</code> 参数，则结果类型为 <code>Type</code> 。
否则，由<code>Type</code>类型来构建一个不带<code>this</code>参数的类型。
泛型会被忽略，并且只有最后的重载签名会被采用。</p>
<h3 id="例子-14"><a class="header" href="#例子-14">例子</a></h3>
<pre><code class="language-ts">function toHex(this: Number) {
    return this.toString(16);
}

const fiveToHex: OmitThisParameter&lt;typeof toHex&gt; = toHex.bind(5);

console.log(fiveToHex());
</code></pre>
<h2 id="thistypetype"><a class="header" href="#thistypetype"><code>ThisType&lt;Type&gt;</code></a></h2>
<p>这个工具不会返回一个转换后的类型。
它做为上下文的<a href="../handbook/functions.html#this"><code>this</code></a>类型的一个标记。
注意，若想使用此类型，必须启用<code>--noImplicitThis</code>。</p>
<h3 id="例子-15"><a class="header" href="#例子-15">例子</a></h3>
<pre><code class="language-typescript">// Compile with --noImplicitThis

type ObjectDescriptor&lt;D, M&gt; = {
    data?: D;
    methods?: M &amp; ThisType&lt;D &amp; M&gt;; // Type of 'this' in methods is D &amp; M
};

function makeObject&lt;D, M&gt;(desc: ObjectDescriptor&lt;D, M&gt;): D &amp; M {
    let data: object = desc.data || {};
    let methods: object = desc.methods || {};
    return { ...data, ...methods } as D &amp; M;
}

let obj = makeObject({
    data: { x: 0, y: 0 },
    methods: {
        moveBy(dx: number, dy: number) {
            this.x += dx; // Strongly typed this
            this.y += dy; // Strongly typed this
        },
    },
});

obj.x = 10;
obj.y = 20;
obj.moveBy(5, 5);
</code></pre>
<p>上面例子中，<code>makeObject</code>参数里的<code>methods</code>对象具有一个上下文类型<code>ThisType&lt;D &amp; M&gt;</code>，因此<code>methods</code>对象的方法里<code>this</code>的类型为<code>{ x: number, y: number } &amp; { moveBy(dx: number, dy: number): number }</code>。</p>
<p>在<code>lib.d.ts</code>里，<code>ThisType&lt;T&gt;</code>标识接口是个简单的空接口声明。除了在被识别为对象字面量的上下文类型之外，这个接口与一般的空接口没有什么不同。</p>
<h2 id="操作字符串的类型"><a class="header" href="#操作字符串的类型">操作字符串的类型</a></h2>
<p>为了便于操作模版字符串字面量，TypeScript 引入了一些能够操作字符串的类型。
更多详情，请阅读<a href="../handbook-v2/type-manipulation/template-literal-types.html#%E5%9B%BA%E6%9C%89%E5%AD%97%E7%AC%A6%E4%B8%B2%E6%93%8D%E4%BD%9C%E7%B1%BB%E5%9E%8B">模版字面量类型</a>。</p>

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